The duo has been sued over their No. 1 hit over alleged copyright infringement, according to court documents acquired by EW. Singer-songwriter White Hinterland, whose real name is Casey Dienel, claims “Sorry” infringes the copyright of her 2014 song “Ring the Bell.” Warner-Tamerlane Publishing Corp. and Universal Music are also named in the suit.

“The identical and/or striking similarity of ‘Sorry’ to Plaintiff’s song ‘Ring the Bell’ surpasses the realm of generic coincidence and independent creation,” the complaint reads.

The alleged indiscretion comes in the introduction of both songs, according to the suit: “Ring the Bell” begins with ascending vocal flourishes, which sound similar to those at the top of “Sorry.” The Bieber-Skrillex collaboration came out in October 2015, more than a year after “Ring the Bell.”

“To write, create, produce, and record the song ‘Sorry,’ the Defendants knowingly and unlawfully copied original, protectable elements of the musical composition of ‘Ring the Bell’ and unlawfully sampled Plaintiff’s protectable sound recording of ‘Ring the Bell,’” a portion of the lawsuit reads. Dienel’s lawsuit also goes into a music theory explanation of how the two songs compare.

The complaint alleges Dienel’s camp sent out a letter to Bieber’s informing them of infringement — along with a musicology report — but there was no response.

Dienel seeks damages, a declaration of copyright infringement, and an injunction to prevent further alleged copyright infringement of “Ring the Bell.’

Reps for Bieber, Skrillex, and Dienel did not immediately respond to EW’s request for comment.